Apache Velocity Template Engine support

Add the Apache Velocity Template Engine support.

The feature.

- Iteration support of Scala Collection, Option(#foreach directive)
- Support of key access to the Scala Map($map['key'], $map.key)
- Rewrite Map#get(key) to Map.getOrElse(key, nul)
- Rewrite Seq#get(index) to Seq.apply(index)
- Rewrite Option#get to Option.getOrElse(nul)
- Easy access Scala class property(ex. val, var, no arguments def)
- Support for velocity-tools(configuration: /WEB-INF/velocity.properties,/WEB-INF/tools.xml)
Is really `GenSeqLike` reasonable here?